Spark plug with improved insulator means



Aug. 10, 1954 F. E. BERSTLER SPARK PLUG WITH IMPROVED INSULATOR MEANSFiled Nov. 19 1951 Fran 0/5 E. Bersfler 1N VEN TOR.

Patented Aug. 10, 1954 SPARK PLUG WITH IMPROVED IN SULATOR MEANS FrancisE. Berstler, Middletown, Pa., assignor of one-third to Charles V. Hoke,Hummelstown, and one-third to Ezra 0. Brubaker, Elizabethtown, Pa.

Application November 19, 1951, Serial No. 257,018

4 Claims. (Cl. 123-169) The present invention relates to certain new anduseful improvements in spark plugs and has to do with a plug which isvirtually leak-proof, whereby to prevent electrical current leakage andfurther to prevent gas leakage between the center or positive electrodeand insulating jacket therefor as well as between said jacket and thecomplemental base and shell portions of the plug proper.

More specifically stated, one phase of the overall improved plug has todo with properly located leak-proofin gaskets or packing rings and themanner in which they are situated between the screw-threaded base andcoacting portion of the insulator means.

Another object of the invention is to provide greatly improved insulatormeans which is structurally unique in that it is characterized by twocomplemental sections of dielectric material, said sections beingsusceptible of practical and expedient manufacture with the coactingends of the sections telescopically interconnected to provide aleak-proof joint between themselves.

A further object of the invention is to provide insulator means whereinone section has a reduced lower end portion with associated recess meansand wherein the other end is also provided with recess means, saidsection being axially bored and screw-threaded and being of a kind andgrade of dielectric material which makes it possible and practical toproduce the bore with a boring machine and to thereafter thread the borewithout breakage or fracture and, at the same time, providing precisionthreads for direct screwing of a screw-threaded electrode shank therein.

A still further object of the invention is to provide a sectionalinsulating construction or means wherein the remaining or complementalsection is of the same kind or grade of material and takes the form of asimple cylindrical tube or sleeve, the latter being cut to desiredlength from a long pre-formed tube, whereby to thus provide insulatormeans which meets the requirement and needs of manufacturers to anextent long desired in this line of endeavor.

Then, too, novelty is predicted on the two-part insulator means with theparts constructed as stated, in combination with a center or positiveelectrode having a reduced screw-threaded shank for coaction with thefirst named section and an enlarged head fitting the bore of the secandnamed section, said head having a simple screw-driver kerf which isaccessibly located in the bore of the second section to permit theelectrode to be adjusted relative to said sections.

Other objects and advantages will become more readily apparent from thefollowin specification taken in conjunction with the drawings andsubjoined claims.

In the accompanying sheet of drawings wherein like numerals are employedto designate like parts throughout the views:

Figure 1 is an assembly view with parts in section and other parts inelevation and showing a complete operative spark plug constructed inaccordance with the principles of the instant invention;

Figure 2 is a sectional view of the sections which go to make up oneform of insulator means; and

Figure 3 is a like sectional view showing a modified construction of thestated insulator means.

Reference is now made to Figure 1 wherein the base of the plug isdenoted by the numeral 4. This is a somewhat conventional type ofmetallic base and includes a body portion 5 with a reduced lower endportion 8 externally screw-threaded at It. The axial bore of the base isinternally screwthreaded at the upper end, as at l2. The lower end ofthe bore in the base is reduced in crosssection, as at it and theintermediate portion of the bore is formed. with an annular channel Itin which a gasket or packing ring 1 8 of compres sible material islocated. The cross section of the gasket is less than the depth of thechannel, as shown. The inner wall 20 of the channel provides aninterlocking lip in a manner to be described.

The upper part of the plug body takes the form of a somewhatconventional cylindrical shell 22 which is also of metal, the upper endbeing externally screw-threaded at 24 and the lower end externallyscrew-threaded at 26 and screwed into the threads 12 in the base. Thenumerals 28-23 designate spanner wrench socket members. The numeral 30denotes a screw cap which is threaded on the upper end 24.

The two-part insulator means comprises a lower or base section 32 and acomplemental upper section 34. The base section, by itself is best shownin Figure 2 wherein it will be seen that it comprises a cylindrical bodyportion 36 having a reduced lower end portion 38 and having an annulargroove 4!} in said lower end providing a lip 42. There is a secondchannel 44 in the flat upper end of the body. These channels constituterecess means hereinafter referred to in the claims. This insulatorsection is provided with an axial screw-threaded bore 46. The uppersection 34 is a simple cylindrical tube or sleeve whose bore 48' is adiameter considerably greater than the screw threaded bore 46. Theoutside diameter of the tube or sleeve is such that the lower endthereof fits telescopically in a leak-proof manner into the groove 44.In the assembly view in Figure 1 it will be seen that the lip 2Q of thebase extends into the channel it and the lip 42 in the insulator sectionextends into the channel l6 thereby providing an interlocking jointwhich is rendered substantially leak-proof by the associatedcompressible packing ring It in an obvious manner.

There is a second compressible gasket ring 5.9 and this encircles thelower end :portion of the insulator sleeve 34, rests upon the fiat upperend of the insulator section 32 and is interposed between the latter,the lower end of the shell .22 and the surrounding wall of the body 6,whereby to provide a second leakproof seal or 'ioi-nt.

The positive or center electrode comprises a reduced screw threaded stemor shank 5.2 which is adjustably threaded through the nor-e45. Thisterminates in a contact cooperating with the negative electrodes orcontacts 55-515 ion the base extension e. The upper end of the electrodeis termed into a large cylindrical head .58 which fits with requisitenicety into the bore of the upper insulated section or sleeve 34. The upend of the head is provided with a screw :driver kerf which .isaccessible for adjusting the electrode and consecuently adjusting thecontacts 5 and 55.

The conductor denoted :by the numeral 62 and is provided with a somewhatconventional adaptor and fitting 6 2 having a retaining flange B S heldin place by the cap 35 and :a reduced portion 518 extending into thebore of the insulator sleeve and the desired electrical connection withthe electrode head is made by coil spring NJ.

At this point in the description it to be explained that the sections.32 and 34 of the electrode means may be .of the same kind of materialalthough this is not absolutely essential. The upper section should bemade "from strong dielectric material which can be turned out in longtubes and the "tubes then severed into sections of the desired size,whereby to render the manufacturing step of :a two-part insulatorconstruction feasible and practical. It is to be .remembered that mostinsulators are of one-piece construction. Here the insulator is made upof two sections 32 and with the sections fitting together by way of therecess means 44. More importantly, the section 32 must be made ofmaterial of special mineral content, of a material which permits saidsection 32 to be satisfactorily mach-inedor otherwise iormed to theshape shown in Figure 2. What is more, the material must, of necessity,lee-substantially fracture proof for it is, as stated, a primary objectof the invention to utilize an insulator section Whose axial bore may bemachined with .no likelihood that the walls of the bore will fracture orbreak and which, in addition, has to be such that .it may be tapped witha threading-die to produce threads which ar accurate in gauge and kindas would be the case if said section 32 were of metal or some othermaterial which is susceptible of being precision bored and tapped. Theseproperties are not found in porcelain or any other insulators ofequivalent material generally known. Since the section 3&- does not haveto be machined but may be molded it does not necessarily have to be ofthe same of material as the companion section 32. This is an importantaspect of the overall problem because the part 32 will be of expensivematerial while the part 34 can be comparatively inexpensive. But what isof chief importance, the insulator is made up of independent readilyassembled sections which lend themselves to the efiective use depictedin Figure l of the drawings.

In the modificationseen in Figure 3 the sleeve section is of insulationmaterial and denoted by the numeral 34a, the bore being denoted at @811.The structural difierence here is that the lower end '52 is reduced toprovide an endless shoulder 34, these features 12 and 14 fitting intothe stepped recesses PM and i8 respectively, in the section $20..Otherwise, this part is the same as 32. Therefore, the same numeralsused in Figure 2 are usedlikewise in Figure 3.

This invention is an improvement on the subjec matter disclosed inco-pending application Serial No. 185,977 filed September 21, 1950, now

Patent No. 2,626,595.

tain .a clear nnderstandin-g .of the invention after considering thedescription in connection with the drawings. Therefore, a more lengthydescription is regarded as unnecessary.

Minor changes in the shape, size and arrangement of details comingwithin the field of inven- .tion claimed may be resorted to in actualpractice, if desired.

.Ha-vi-ng described the invention what is claimed as new is:

1. A spark plug comprising an axially bored metallic base provided withexternal screw threads and negative electrode means at one end andinternal screw-thceads at the other end, said here .being reduced indiameter .at the externally screw thrcaded end and provided with an au-ular channel, .a compressible gasket mount- .ed in said channel, anaxially aligned metallic cylindrical shell having escrow-threaded rendscrewed into the internal screw-threads said base, a first insulatorsection fitted wholly :into the .bore in said base and having a reduced10W- er end portion telescoping into the reduced end of said bore andfurther having its lower end formed with an annular channel interlockedwith the first named annular channel and coacting with said gasket .toprovide a sealed joint, the upper end of said insulator section havinggroove means, a second insulator section of .a length greater than thelength of said first section, fitted into said shell and having lowerend telescopin into said groove means and having precision gas-proofengagement with said first section, additional gasket means encirclingsaid second section and jammed between the latter, the first section,and lower end of said shell, said second section being of uniformdiameter from end to and of an aouwlde diameter less than the outsidediameter of said section, said first insulator section being of a hard.iractureepioof machinaible dielectric material which is susceptible ofbeing precision machined to assume a predetermined external shape, alsomachinebored, said bore being precisely 'screwwhreaded,

and an adjustable positive electrode having an accurately screw-threadedscrewed into and all the way through and beyond said bore.

2. For use in 'a spark plug, a two-part insulator comprising amachine-bored and screw-threaded tbase section and a companion tubularsecond section, the latter being of uniform cross-sectional diameterfrom end to end and of a length greater than said base section, theupper end of said base section having groove means exactingly machinedtherein, the lower end of said second section fitting telescopically andaccurately in said groove means and having positive leak-proofengagement with said base section, and the lower end of said basesection having an annular channel and a reduced portion extendingaxially beyond said lower end, said base section consisting of a gradeand kind of fracture-proof dielectric mineral which is capable, withoutbreakage, of being machine-shaped exteriorly.

3. The structure defined in claim 2 and the combination therewith of apositive electrode having a reduced screw-threaded shank screwed intothe bore of said base section and an enlarged head portion fittingsnugly in the bore of said second section, said head having anaccessible screwdriver kerf for adjusting said electrode relative tosaid sections.

4. For use in a spark plug, a sectional insulator comprising a firstbase-forming section having a body of cylindrical cross-section, theupper end of said body being flat and provided with an endless grooveconcentric to the lengthwise axis of the body, the lower end of saidbody being reduced in cross-section and providing an axial extension,said lower end of the body being provided with an endless grooveconcentrically encircling that part of the reduced portion which isjoined with the body portion, said section being of rigid fracture-proofnon-metallic dielectric mineral material which is inherently capable ofbeing formed to a given shape and then machined exteriorly to providethe desired over-all exterior shape, said section being machine-boredaxially and then tapped and screw-threaded to provide a screw-threadedbore opening through the upper and lower ends, and a second complementalsection, the latter being a cylindrical tube of a length greater thansaid first section and of uniform diameter from end-to-end and of anexternal diameter less than the external diameter of the body of thefirst section and having a bore opening through its opposite ends and ofa diameter greater than the bore in said first named section, the lowerend of said second section fitting telescopically into said groove andproviding a snug gas-proof junctural connection between the sections.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 898,427 Benoist Sept. 15, 1908 927,704 Baskin 1. July 13, 19091,225,467 Miller May 8, 1917 1,337,679 Williams Apr. 20, 1920 1,801,023Rohde Apr. 14, 1931 2,053,369 Jefiery Sept. 8, 1936 2,351,543 Race June13, 1944 2,368,889 Setterblade Feb. 6, 1945

